1. Field of the Invention
The present invention is broadly concerned with improved salt tolerant alfalfa cultivars. More particularly, the invention pertains to novel field selected cultivars of Medicago sativa L. which exhibit enhanced germination and plant vigor when grown in salty soils.
2. Description of the Prior Art
Alfalfa (Medicago sativa L., also known as lucerne) is one of the world's most valuable forage legumes. It is grown for hay, pasture and silage, and is valued highly as a livestock feed. Alfalfa originated in the Near East, in the area extending from Turkey to Iran and north into the Caucasus. From the great diversity of forms within the genus Medicago, two species, M. sativa and M. falcata, have become important forage plants. These species are mainly tetraploid, with 32 chromosomes, although diploid forms are known. Alfalfa species are composed of ecotypes, population complexes adapted to the environment of a given climatic region or to definite habitats within a region.
Alfalfa is a herbaceous perennial legume characterized by a deep tap root showing varying degrees of branching. Erect or semi-erect stems, bearing an abundance of leaves, grow to a height of 2-3 feet. The number of stems arising from a single woody crown may vary from just a few to 50 or more. New stems develop when older ones mature or have been cut or grazed. Flowers are borne on axillary racemes which vary greatly in size and number of flowers. Flower color is predominantly purple, or bluish-purple, but other colors occur. The fruit is a legume, or pod, usually spirally coiled in M. sativa. Seeds are small, with about 220,000/lb., and the color varies from yellow to brown. Alfalfa is widely adapted to temperature and soil conditions, save for humid tropical conditions. Reproduction in alfalfa is mainly by cross-fertilization, but substantial self-pollination may also occur. Cross-pollination is effected largely by bees.
The commercial production of seeds for growing alfalfa plants normally involves four stages, the production of breeder, foundation, certified and registered seeds. Breeder seed is the initial increase of seed of the strain which is developed by the breeder and from which foundation seed is derived. Foundation seed is the second generation of seed increase and from which certified seed is derived. Certified seeds are used in commercial crop production and are produced from foundation or certified seed. Foundation seed normally is distributed by growers or seedsmen as planting stock for the production of certified seed.
Although alfalfa production is widely distributed, essentially all commercially available cultivars have very poor salt tolerance. As a consequence, it is very difficult to achieve adequate alfalfa yields (or even stands) in salty soil found in areas such as Southern California, Arizona, New Mexico and Texas. Salt tolerant varieties have heretofore not been available on the commercial market. Certain salt tolerant germplasm releases have been made which are useful in variety development. One such prior germplasm release, AZ-Germ Salt II was a laboratory development and has been noted for its ability to germinate in saline environments.
There is accordingly a real and unsatisfied need in the art for improved salt tolerant alfalfa cultivars which have the necessary degree of germination capacity and post-germination vigor which will make it possible to extend substantial alfalfa production to high salt soils.